best thing you can do is experiment.
if youve got a dslr, get a couple of off camera flashes. lighting is key, and having some flashes lets you control the lighting.
what i do is put the camera on a tripod and take multiple exposures with the flashes in different locations, then merge all the layers together in photoshop.

obviously, not everyone has access to a dslr and flashes, so youll be needing to use available light. the best light happens at sunrise and sunset. its soft, has good tone and comes in at an angle. unless you want a silhouette, you'll want the side of the car youre photographing to face the sun. make sure youre at an angle where you don't get your reflection or shadow on the car. the best looking photos (IMO) have the sky reflected in the windows.

another thing you can do is wait till its a bit darker, put the camera on a tripod, and take a long exposure (30 seconds or so). walk around the car with a light of some kind and shine it at the parts you want to highlight. experiment with different coloured and shaped lights, lighting different areas and moving the light around at different angles.

the most important part is to experiment, practice, and keep at it. theres is no formula on how to take a good car picture, or on how to take a good picture of anything for that matter, there are merely things to keep in mind as you experiment.

I've got some old instant camera photos that I have tried to scan, but they came out real grainy. What is the trick to doing a better job? How much resolution should i use and what size should the picture be to post on this forum through Photo Bucket or is it just trial and lots of error? I have no negatives. How about just taking another picture of the photo with a digital camera?
Here is a digital photo of a picture, much better than scanning.

I think i made every single mistake pointed out in this thread but i still think it looks cool

I took in the middle of nowhere between Chile and Argentina.

You think your picture looks cool because it is! While you have not made the car the subject, like most people are giving advice for, the narrative (sorry, I'm an art major) is great. You are showing the viewer a piece of your journey in South America and the landscape is just as important as the vehicle.
Also, you pulled off the road; good move, especially on that blind hill.
I like that the horizon line is just below or at the bottom of the windows. Not sure if you did this on purpose but having the sky in the windows brings the (under-lit) car into the viewer's attention. I do think it would be worth brightening the car a little in Photoshop; just a little.
BTW, who the heck were you gonna call when it broke??

...
also small aparature can help you, leaving the background more out of focus.

I just want to point out that it's a larger aperture that helps, but larger aperture = smaller number. Knowing this makes a difference.

Fox

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88 745 Turbo w/ full IPD springs/sways/bilstein HD's, a replacement 95 turbo motor (now with over 300k on it) running through an m46 to an open diff. Can you say peg legged?
95 BMW 540i6 - wallet vampire
86 RX7
....... The wagon's the quickest to 60 , then gets raped by the 540i. :(